Formylated chemotactic peptides, with endogenous Tc-99m binding sites, will be developed for use in localizing abscesses, inflammations, and infections. The peptides are designed to have the biological function located at one end of the molecule, and the Tc-99m binding site at the other end of the molecule. In Phase I the chemotactic peptide analogs will be formulated in single-step, direct labeling kits, and used in animal studies to localize infections and inflammations. Initial studies will include analysis of labeling efficiency and definition of optimal labeling conditions, and binding of Tc-99m-labeled formyl peptides to lymphocytes. In Phase II, comparative localization studies will be conducted, using In- 111-oxine-labeled lymphocytes and Tc-99m-human gamma globulin as reference materials.